CQI reporting for MIMO transmissionin a wireless communication system

ABSTRACT

Techniques for determining and reporting channel quality indicator (CQI) information are described. A user equipment (UE) may determine a transmit power per channelization code, P OVSF , based on the available transmit power and a designated number of channelization codes, e.g., by uniformly distributing the available transmit power across all transport blocks and all of the designated number of channelization codes. The UE may estimate SINRs of multiple transport blocks based on P OVSF , determine CQI indices for the transport blocks based on the SINRs, and send the CQI indices to a Node B. The Node B may send multiple transport blocks to the UE based on the CQI indices. The Node B may send the transport blocks (i) with the designated number of channelization codes at P OVSF  or (ii) with a second number of channelization codes at P OVSF , with the transport block sizes being scaled based on the designated and second numbers of channelization codes.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present Application for Patent claims priority to Provisional U.S.Application Ser. No. 60/884,202, entitled “CQI REPORTING FOR FDD MIMO,”filed Jan. 9, 2007, assigned to the assignee hereof, and expresslyincorporated herein by reference.

BACKGROUND

I. Field

The present disclosure relates generally to communication, and morespecifically to techniques for reporting channel quality indicator (CQI)information in a wireless communication system.

II. Background

In a wireless communication system, a Node B may utilize multiple (T)transmit antennas for data transmission to a user equipment (UE)equipped with multiple (R) receive antennas. The multiple transmit andreceive antennas form a multiple-input multiple-output (MIMO) channelthat may be used to increase throughput and/or improve reliability. Forexample, the Node B may transmit up to T data streams simultaneouslyfrom the T transmit antennas to improve throughput. Alternatively, theNode B may transmit a single data stream from all T transmit antennas toimprove reception by the UE. Each data stream may carry one transportblock of data in a given transmission time interval (TTI). Hence, theterms “data stream” and “transport block” may be used interchangeably.

Good performance (e.g., high throughput) may be achieved by sending eachtransport block at the highest possible rate that still allows the UE toreliably decode the transport block. The UE may estimatesignal-to-interference-and-noise ratios (SINRs) of each possiblecombination of transport blocks that might be transmitted and may thendetermine CQI information based on the estimated SINRs of the bestcombination of transport blocks. The CQI information may convey a set ofprocessing parameters for each transport block. The UE may send the CQIinformation to the Node B. The Node B may process one or more transportblocks in accordance with the CQI information and send the transportblock(s) to the UE.

Data transmission performance may be dependent on accurate determinationand reporting of CQI information by the UE. There is therefore a need inthe art for techniques to accurately determine and report CQIinformation.

SUMMARY

Techniques for determining and reporting CQI information for a MIMOtransmission are described herein. In an aspect, a UE may determine CQIinformation based on a transmit power per channelization code, P_(OVSF),that is known by both the UE and a Node B. For a MIMO transmission sentusing code division multiplexing, the SINR of a transport block may bedependent on P_(OVSF) but may not be a linear function of P_(OVSF) . Theuse of a known P_(OVSF) may improve accuracy in SINR estimation. The UEmay determine P_(OVSF) based on (i) the available transmit power, whichmay be obtained via signaling from the Node B, and (ii) a designatednumber of channelization codes, which may be a known value or obtainedvia signaling. The UE may assume a uniform distribution of the availabletransmit power across multiple (e.g., two) transport blocks and alsoacross the designated number of channelization codes to obtain P_(OVSF).

The UE may then estimate the SINRs of the transport blocks based onP_(OVSF) . The UE may determine CQI indices for the transport blocksbased on the SINRs and a CQI mapping table for the designated number ofchannelization codes. The UE may send the CQI indices as CQI informationto the Node B.

The Node B may send multiple transport blocks in a MIMO transmission tothe UE based on the CQI information received from the UE. In one design,the Node B may send the transport blocks with the designated number ofchannelization codes at P_(OVSF). In another design, the Node B may sendthe transport blocks with a second number of channelization codes atP_(OVSF) and may scale the sizes of the transport blocks based on thedesignated number of channelization codes and the second number ofchannelization codes. In yet another design, the Node B may scaleP_(OVSF) based on the designated number of channelization codes and thesecond number of channelization codes. The Node B may then send thetransport blocks with the second number of channelization codes at thescaled P_(OVSF).

Various aspects and features of the disclosure are described in furtherdetail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system.

FIG. 2 shows a block diagram of a Node B and a UE.

FIG. 3 shows a timing diagram for a set of physical channels.

FIG. 4 shows a process for determining CQI information.

FIG. 5 shows a design for sending the CQI information.

FIG. 6 shows a process performed by the UE.

FIG. 7 shows a process performed by the Node B.

DETAILED DESCRIPTION

The techniques described herein may be used for various wirelesscommunication systems such as Code Division Multiple Access (CDMA)systems, Time Division Multiple Access (TDMA) systems, FrequencyDivision Multiple Access (FDMA) systems, Orthogonal FDMA (OFDMA)systems, Single-Carrier FDMA (SC-FDMA) systems, etc. The terms “system”and “network” are often used interchangeably. A CDMA system mayimplement a radio technology such Universal Terrestrial Radio Access(UTRA), cdma2000, etc. UTRA includes Wideband-CDMA (W-CDMA) and otherCDMA variants. cdma2000 covers IS-2000, IS-95 and IS-856 standards. UTRAis part of Universal Mobile Telecommunication System (UMTS), and bothare described in documents from an organization named “3rd GenerationPartnership Project” (3GPP). cdma2000 is described in documents from anorganization named “3rd Generation Partnership Project 2” (3GPP2). Thesevarious radio technologies and standards are known in the art. Forclarity, the techniques are described below for UMTS, and UMTSterminology is used in much of the description below.

FIG. 1 shows a wireless communication system 100 with multiple Node Bs110 and multiple user equipments (UEs) 120. System 100 may also bereferred to as a Universal Terrestrial Radio Access Network (UTRAN) inUMTS. A Node B is generally a fixed station that communicates with theUEs and may also be referred to as an evolved Node B (eNode B), a basestation, an access point, etc. Each Node B 110 provides communicationcoverage for a particular geographic area and supports communication forthe UEs located within the coverage area. A system controller 130couples to Node Bs 110 and provides coordination and control for theseNode Bs. System controller 130 may be a single network entity or acollection of network entities.

UEs 120 may be dispersed throughout the system, and each UE may bestationary or mobile. A UE may also be referred to as a mobile station,a terminal, an access terminal, a subscriber unit, a station, etc. A UEmay be a cellular phone, a personal digital assistant (PDA), a wirelessdevice, a handheld device, a wireless modem, a laptop computer, etc.

FIG. 2 shows a block diagram of a design of one Node B 110 and one UE120. In this design, Node B 110 is equipped with multiple (T) antennas220 a through 220 t, and UE 120 is equipped with multiple (R) antennas252 a through 252 r. A MIMO transmission may be sent from the T transmitantennas at Node B 110 to the R receive antennas at UE 120.

At Node B 110, a transmit (TX) data and signaling processor 212 mayreceive data from a data source (not shown) for all scheduled UEs.Processor 212 may process (e.g., format, encode, interleave, and symbolmap) the data for each UE and provide data symbols, which are modulationsymbols for data. Processor 212 may also process signaling and providessignaling symbols, which are modulation symbols for signaling. A spatialmapper 214 may precode the data symbols for each UE based on a precodingmatrix or vector for that UE and provide output symbols for all UEs. ACDMA modulator (MOD) 216 may perform CDMA processing on the outputsymbols and signaling symbols and may provide T output chip streams to Ttransmitters (TMTR) 218 a through 218 t. Each transmitter 218 mayprocess (e.g., convert to analog, filter, amplify, and frequencyupconvert) its output chip stream and provide a downlink signal. Tdownlink signals from T transmitters 218 a through 218 t may be sent viaT antennas 220 a through 220 t, respectively.

At UE 120, R antennas 252 a through 252 r may receive the downlinksignals from Node B 110 and provide R received signals to R receivers(RCVR) 254 a through 254 r, respectively. Each receiver 254 may process(e.g., filter, amplify, frequency downconvert, and digitize) itsreceived signal and provide samples to a channel processor 268 and anequalizer/CDMA demodulator (DEMOD) 260. Processor 268 may derivecoefficients for a front-end filter/equalizer and coefficients for oneor more combiner matrices. Unit 260 may perform equalization with thefront-end filter and CDMA demodulation and may provide filtered symbols.A MIMO detector 262 may combine the filtered symbols across spatialdimension and provide detected symbols, which are estimates of the datasymbols and signaling symbols sent to UE 120. A receive (RX) data andsignaling processor 264 may process (e.g., symbol demap, deinterleave,and decode) the detected symbols and provide decoded data and signaling.In general, the processing by equalizer/CDMA demodulator 260, MIMOdetector 262, and RX data and signaling processor 264 is complementaryto the processing by CDMA modulator 216, spatial mapper 214, and TX dataand signaling processor 212, respectively, at Node B 110.

Channel processor 268 may estimate the response of the wireless channelfrom Node B 110 to UE 120. Processor 268 and/or 270 may process thechannel estimate to obtain feedback information, which may includeprecoding control indicator (PCI) information and CQI information. ThePCI information may convey the number of transport blocks to send inparallel and a specific precoding matrix or vector to use for precodingthe transport block(s). A transport block may also be referred to as apacket, a data block, etc. The CQI information may convey processingparameters (e.g., the transport block size and modulation scheme) foreach transport block. Processor 268 and/or 270 may evaluate differentpossible precoding matrices and vectors that can be used for datatransmission and may select a precoding matrix or vector that canprovide the best performance, e.g., the highest overall throughput.Processor 268 and/or 270 may also determine the CQI information for theselected precoding matrix or vector.

The feedback information and data to send on the uplink may be processedby a TX data and signaling processor 280, further processed by a CDMAmodulator 282, and conditioned by transmitters 254 a through 254 r togenerate R uplink signals, which may be transmitted via antennas 252 athrough 252 r, respectively. The number of transmit antennas at UE 120may or may not be equal to the number of receive antennas. For example,UE 120 may receive data using two antennas but may transmit the feedbackinformation using only one antenna. At Node B 110, the uplink signalsfrom UE 120 may be received by antennas 220 a through 220 t, conditionedby receivers 218 a through 218 t, processed by an equalizer/CDMAdemodulator 240, detected by a MIMO detector 242, and processed by an RXdata and signaling processor 244 to recover the feedback information anddata sent by UE 120. The number of receive antennas at Node B 110 may ormay not be equal to the number of transmit antennas.

Controllers/processors 230 and 270 may direct the operation at Node B110 and UE 120, respectively. Memories 232 and 272 may store programcode and data for Node B 110 and UE 120, respectively. A scheduler 234may schedule UEs for downlink and/or uplink transmission, e.g., based onthe feedback information received from the UEs.

In UMTS, data for a UE may be processed as one or more transportchannels at a higher layer. The transport channels may carry data forone or more services such as voice, video, packet data, etc. Thetransport channels may be mapped to physical channels at a physicallayer. The physical channels may be channelized with differentchannelization codes and may thus be orthogonal to one another in thecode domain. UMTS uses orthogonal variable spreading factor (OVSF) codesas the channelization codes for the physical channels.

3GPP Release 5 and later supports High-Speed Downlink Packet Access(HSDPA), which is a set of channels and procedures that enablehigh-speed packet data transmission on the downlink. For HSDPA, a Node Bmay send data on a High Speed Downlink Shared Channel (HS-DSCH), whichis a downlink transport channel that is shared by all UEs in both timeand code. The HS-DSCH may carry data for one or more UEs in each TTI.For UMTS, a 10 millisecond (ms) radio frame is partitioned into five2-ms subframes, each subframe includes three slots, and each slot has aduration of 0.667 ms. A TTI is equal to one subframe for HSDPA and isthe smallest unit of time in which a UE may be scheduled and served. Thesharing of the HS-DSCH may change dynamically from TTI to TTI.

Table 2 lists some downlink and uplink physical channels used for HSDPAand provides a short description for each physical channel.

TABLE 1 Link Channel Channel Name Description Downlink HS-PDSCH HighSpeed Physical Carry data sent on Downlink Shared the HS-DSCH forChannel different UEs. Downlink HS-SCCH Shared Control Carry signalingfor Channel for HS-DSCH the HS-PDSCH. Uplink HS-DPCCH Dedicated PhysicalCarry feedback for Control Channel downlink transmission for HS-DSCH inHSDPA.

FIG. 3 shows a timing diagram for the physical channels used for HSDPA.For HSDPA, a Node B may serve one or more UEs in each TTI. The Node Bmay send signaling for each scheduled UE on the HS-SCCH and may senddata on the HS-PDSCH two slots later. The Node B may use a configurablenumber of 128-chip OVSF codes for the HS-SCCH and may use up to fifteen16-chip OVSF codes for the HS-PDSCH. HSDPA may be considered as having asingle HS-PDSCH with up to fifteen 16-chip OVSF codes and a singleHS-SCCH with a configurable number of 128-chip OVSF codes. Equivalently,HSDPA may be considered as having up to fifteen HS-PDSCHs and aconfigurable number of HS-SCCHs, with each HS-PDSCH having a single16-chip OVSF code and each HS-SCCH having a single 128-chip OVSF code.The following description uses the terminology of a single HS-PDSCH anda single HS-SCCH.

Each UE that might receive data on the HS-PDSCH may process up to four128-chip OVSF codes for the HS-SCCH in each TTI to determine whethersignaling has been sent for that UE. Each UE that is scheduled in agiven TTI may process the HS-PDSCH to recover data sent to that UE. Eachscheduled UE may send either an acknowledgement (ACK) on the HS-DPCCH ifa transport block is decoded correctly or a negative acknowledgement(NACK) otherwise. Each UE may also send PCI and CQI information on theHS-DPCCH to the Node B.

FIG. 3 also shows timing offsets between the HS-SCCH, the HS-PDSCH, andthe HS-DPCCH at a UE. The HS-PDSCH starts two slots after the HS-SCCH.The HS-DPCCH starts approximately 7.5 slots from the end of thecorresponding transmission on the HS-PDSCH.

A UE may send CQI information to allow a Node B to process and transmitdata to the UE. In general, CQI information may be sent for any numberof transport blocks or data streams. For clarity, much of thedescription below assumes that one or two transport blocks may be sentin a given TTI and that the CQI information may be for one or twotransport blocks. The CQI information should have the followingcharacteristics:

-   -   Allow for reporting of a CQI index for each transport block,    -   Provide sufficient number of levels for the CQI index for each        transport block, and    -   Support flexible reporting of CQI information for one or two        transport blocks.

The Node B may transmit two transport blocks to the UE using one ofmultiple possible precoding matrices or may transmit a single transportblock using one column/vector of one of the possible precoding matrices.The UE may evaluate data performance for different possible precodingmatrices and vectors that can be used by the Node B for datatransmission to the UE. For each precoding matrix or vector, the UE mayestimate the quality of each transport block, which may be given by anysuitable metric. For clarity, the following description assumes that thequality of each transport block is given by an equivalent SINR for anadditive white Gaussian noise (AWGN) channel, which is referred to assimply SINR in the description below. The UE may determine dataperformance (e.g., the overall throughput) for each precoding matrix orvector based on the SINR(s) of all transport block(s). After evaluatingall possible precoding matrices and vectors, the UE may select theprecoding matrix or vector that provides the best data performance.

For each possible precoding matrix, the UE may estimate the SINRs of twotransport blocks that may be sent in parallel with that precodingmatrix. The transport block with the higher SINR may be referred to asthe primary transport block, and the transport block with the lower SINRmay be referred to as the secondary transport block. The SINR of eachtransport block may be dependent on various factors such as (i) thetransmit power available for data transmission on the HS-PDSCH, (ii) thenumber of OVSF codes used for the data transmission, (iii) channelconditions, which may be given by channel gains and noise variance, (iv)the type of receiver processing performed by the UE, (v) the order inwhich the transport blocks are recovered if successive interferencecancellation (SIC) is performed by the UE, and (vi) possibly otherfactors.

The SINR of transport block i, SINR_(i), may be given as:

SINR _(i) =F (P _(OVSF) , X _(i))  Eq (1)

where P_(OVSF) is the transmit power per OVSF code for the HS-PDSCH,

-   -   X_(i) includes all other parameters that affect SINR, and    -   F( ) is an SINR function applicable for the UE.

The SINR function may be dependent on the receiver processing at the UEand may not be a linear function of P_(OVSF) . Thus, if P_(OVSF)increases by G decibel (dB), then the amount of improvement in SINR maynot be accurately known based solely on the G dB increase in P_(OVSF) .This non-linear relationship between P_(OVSF) and SINR may be due tocode-reuse interference, which is interference between two transportblocks using the same OVSF codes. Furthermore, the SINR function may notbe known at the Node B.

In an aspect, the UE may estimate SINR based on a transmit power perOVSF code that is known by both the UE and the Node B. In one design,the known P_(OVSF) may be determined based on knowledge or assumption of(i) the transmit power P_(HSPDSCH) available for data transmission onthe HS-PDSCH, (ii) a designate number of OVSF codes, M, for theHS-PDSCH, and (iii) uniform distribution of the available transmit poweracross the M OVSF codes for each transport block.

The available transmit power P_(HSPDSCH) for the HS-PDSCH may beprovided by higher layer signaling and/or some other mechanism, e.g., ona regular basis or whenever there is a change. In one design, theavailable transmit power P_(HSPDSCH) may be determined as follows:

P _(HSPDSCH) =P _(CPICH)+Γ, in dB  Eq (2)

where P_(CPICH) is the transmit power of a Common Pilot Channel (CPICH),and

-   -   Γ is a power offset that may be signaled by higher layer.

In one design, the available transmit power may be distributed evenly totwo transport blocks, and P_(OVSF) may be the same for both transportblocks. In another design, a particular percentage of the availabletransmit power may be distributed to the primary transport block, theremaining transmit power may be distributed to the secondary transportblock, and P_(OVSF) may be different for the two transport blocks.

In one design, the designated number of OVSF codes, M, to use in thecomputation of P_(OVSF) may be provided by higher layer signaling and/orsome other mechanism, e.g., on a regular basis or whenever there is achange. In another design, M may be assumed to be equal to the maximumnumber of OVSF codes for the HS-PDSCH (i.e., M=15) or equal to someother predetermined value. In any case, P_(OVSF) may be obtained byuniformly distributing the available transmit power across the M OVSFcodes, as follows:

P _(OVSF) =P _(HSPDSCH)−10·log₁₀(2·M), in dB.  Eq (3)

In equation (3), subtraction in dB is equivalent to division in linearunit. The factor of 2 within the log₁₀ term assumes that P_(HSPDSCH) isdistributed evenly between two transport blocks.

The UE may estimate the SINR of each transport block based on P_(OVSF)for that transport block. The UE may then map the SINR of each transportblock to a CQI index based on a CQI mapping table, which may also bereferred to as a CQI indexing table. The CQI mapping table may have Lentries for L possible CQI levels, where L may be any suitable value.Each CQI level may be associated with a set of parameters for atransport block as well as a required SINR. The L CQI levels may beassociated with increasing required SINRs. For each transport block, theUE may select the highest CQI level with a required SINR that is lowerthan the estimated SINR of that transport block. The CQI index for eachtransport block would indicate one of L possible CQI levels.

FIG. 4 shows a process 400 for determining CQI indices for multiple(e.g., two) transport blocks. The transmit power per OVSF code,P_(OVSF), may be determined based on the available transmit power,P_(HSPDSCH), and the designated number of OVSF codes, M, e.g., as shownin equation (3) (block 412). The SINRs of the transport blocks may beestimated based on the transmit power per OVSF code and other parametersand in accordance with an SINR function (block 414). The SINRs of thetransport blocks may be mapped to CQI indices based on a CQI mappingtable (block 416). The CQI indices may be sent to the Node B (block 418)and may be used by the Node B to transmit multiple transport blocks tothe UE.

A CQI mapping table may be defined in various manners. The number ofentries in the table, L, may be selected based on various factors suchas the range of SINRs to be covered by the table, the desiredgranularity between adjacent CQI levels, the number of bits to use forthe CQI information, etc. In one design, L=15, and the CQI mapping tableincludes 15 entries for 15 possible CQI levels. Each CQI level may beassociated with a set of parameters that may include a transport blocksize and a modulation scheme. The set of parameters may also implicitlyor explicitly include other parameters such as code rate.

In general, for a given target block error rate (BLER), a higher coderate and a higher modulation order may be used for higher SINR, and viceversa. A set of modulation schemes may be supported for HSDPA. Thehighest order modulation scheme may be used for higher SINRs, and thelowest order modulation scheme may be used for lower SINRs. A range ofcode rates (e.g., from 1/3=0.333 to 1) may also be supported for HSDPA.A higher code rate (e.g., near 1) provides less redundancy and may beused for higher SINR. Conversely, a lower code rate (e.g., 0.333)provides more redundancy and may be used for lower SINR.

Table 2 shows a CQI mapping table in accordance with one specificdesign. This design assumes (i) the designated number of OVSF codes forthe HS-PDSCH is M=15, (ii) quadrature phase shift keying (QPSK) and16-level quadrature amplitude modulation (16QAM) may be used for HSDPA,and (iii) the code rate can range from 0.333 to 1. In this CQI mappingtable, each CQI level is associated with a specific transport block sizeand a specific modulation scheme. The 15 CQI levels in the table aredefined based on a spacing of approximately 1.0 to 1.5 dB in SINRbetween adjacent CQI levels.

TABLE 2 CQI Mapping Table for M = 15 OVSF codes for HS-PDSCH EquivalentAdditional AWGN SINR CQI Transport Code Offset per symbol Level BlockSize Modulation Rate (in dB) (in dB) 0 4834 QPSK 0.333 −5.0 −1.24 1 4834QPSK 0.333 −3.0 −1.24 2 4834 QPSK 0.333 −1.5 −1.24 3 4834 QPSK 0.333 0−1.24 4 6101 QPSK 0.424 0 0.27 5 7564 QPSK 0.525 0 1.58 6 9210 QPSK0.640 0 3.09 7 10629 QPSK 0.738 0 4.29 8 12488 16QAM 0.434 0 5.70 914936 16QAM 0.519 0 6.86 10 17548 16QAM 0.609 0 8.46 11 20251 16QAM0.703 0 9.75 12 22147 16QAM 0.769 0 11.5 13 24222 16QAM 0.841 0 12.17 1426352 16QAM 0.915 0 13.72

For each required SINR shown in column 6 of Table 2, the modulationscheme and code rate that can maintain a block error rate at or belowthe target BLER may be determined by computer simulation, measurements,etc. As shown in Table 2, the highest code rate of 0.915 and the highestorder modulation scheme of 16-QAM are used for the highest CQI level of14. The code rate drops for each lower CQI level until a code rate of0.434 for CQI level of 8. A lower order modulation scheme of QPSK isused for the next lower CQI level of 7, and the resulting code rate is0.738. The code rate again drops for each lower CQI level until a coderate of 0.333 for CQI level of 3.

The transport block size for each CQI level may be determined asfollows. A TTI covers 7680 chips, and 480 modulation symbols may be sentwith one 16-chip OVSF code in one TTI. A total of 480×15=7200 modulationsymbols may be sent with fifteen 16-chip OVSF codes on the HS-PDSCH inone TTI. For QPSK, two code bits may be sent in each modulation symbol,and a total of 14,400 code bits may be sent in 7200 modulation symbols.For 16QAM, four code bits may be sent in each modulation symbol, and atotal of 28,800 code bits may be sent in 7200 modulation symbols. Thetransport block size is equal to the number of code bits times the coderate.

In one design, when the lowest code rate and the lowest order modulationscheme have been reached, the same transport block size is repeated forall lower CQI levels. In the example shown in Table 2, the transportblock size of 4834 is repeated for CQI levels 0, 1 and 2. The SINRsachieved by the UE for CQI levels 0, 1 and 2 may be lower than therequired SINR for QPSK and code rate 0.333. The expected differencebetween the SINR achieved by the UE for each of CQI levels 0, 1 and 2and the required SINR for CQI level 3 is shown by column 5 of Table 2. Ahigher BLER may result for a transport block sent for CQI level 0, 1 or2, but this transport block may be retransmitted if received in error.In another design, when the lowest code rate and the lowest ordermodulation scheme have been reached, the transport block size may bereduced, and some bits may be repeated to improve reliability. In yetanother design, when the lowest code rate and the lowest ordermodulation scheme have been reached, the number of OVSF codes may bereduced, and the transport block size may be reduced correspondingly.For example, a transport block size of 3172 may be sent with 10 OVSFcodes for CQI level 2, a transport block size of 2212 may be sent with 7OVSF codes for CQI level 1, and a transport block size of 1262 may besent with 4 OVSF codes for CQI level 0.

In general, a CQI mapping table may be defined to cover any range ofSINRs and with any granularity between CQI levels. A CQI mapping tablemay be defined such that (i) the lowest CQI level 0 corresponds to thelowest code rate and the lowest order modulation scheme, (ii) thehighest CQI level 14 corresponds to the highest code rate and thehighest order modulation scheme, and (iii) there are no repeated entriesin the table. A CQI mapping table may be defined to have approximatelyequal delta SINR between neighbor CQI levels. Alternatively, a CQImapping table may be defined to have (i) a smaller delta SINR or finergranularity for a subrange that is more commonly used and (ii) a largerdelta SINR or more coarse granularity for a subrange that is used lessoften.

Table 2 shows one specific design of a CQI mapping table for a case inwhich M=15. CQI mapping tables may also be defined for other values ofM. For example, CQI mapping tables may be defined for 5, 10, and/or someother values of M. For a given value of M, multiple CQI mapping tablesmay also be defined for different ranges of SINRs and/or differentgranularity between CQI levels. If multiple CQI mapping tables areavailable, then one CQI mapping table may be selected for use, e.g., bythe Node B and signaled to the UE, or vice versa.

The UE may map the SINR of each transport block to a CQI index based ona CQI mapping table selected for use. In one design, symmetric OVSF codeallocation is employed, and the same number and same set of OVSF codesis used for two transport blocks. In this design, the CQI mapping tablemay be defined such that the same number of OVSF codes is used for allCQI levels. In another design, asymmetric OVSF code allocation isallowed, and the number of OVSF codes for the secondary transport blockmay be different (e.g., fewer) than the number of OVSF codes for theprimary transport block. In this design, the CQI mapping table may havedifferent numbers of OVSF codes for different CQI levels, e.g., fewerOVSF codes for one or more of the lowest CQI levels. The secondarytransport block may be sent with a subset of the OVSF codes used for theprimary transport block.

If a precoding matrix is selected, then the UE may separately determinetwo CQI indices for two transport blocks to be sent in parallel with theselected precoding matrix. If a precoding vector is selected, then theUE may determine one CQI index for one transport block to be sent withthe selected precoding vector. The UE may send a single CQI value thatcan convey either one CQI index for one transport block or two CQIindices for two transport blocks. With a granularity of 15 CQI levelsfor each CQI index in the case of two transport blocks, a total of15×15=225 CQI index combinations are possible for two transport blocks.If 8 bits are used for the single CQI value, then up to 256−225=31levels may be used for the CQI index for one transport block.

In one design, the single CQI value may be determined as follows:

$\begin{matrix}{{CQI} = \left\{ \begin{matrix}{{15 \times {CQI}_{1}} + {CQI}_{2} + 31} & \begin{matrix}{{when}\mspace{14mu} 2\mspace{14mu} {transport}\mspace{14mu} {blocks}} \\{{are}\mspace{14mu} {preferred}\mspace{14mu} {by}\mspace{14mu} {the}\mspace{14mu} {UE}}\end{matrix} \\{CQI}_{S} & \begin{matrix}{{when}\mspace{14mu} 1\mspace{14mu} {transport}\mspace{14mu} {block}} \\{{is}\mspace{14mu} {preferred}\mspace{14mu} {by}\mspace{14mu} {the}\mspace{14mu} {UE}}\end{matrix}\end{matrix} \right.} & {{Eq}\mspace{14mu} (4)}\end{matrix}$

where CQI_(s) is a CQI index within {0 . . . 30} for one transportblock,

-   -   CQI₁ is a CQI index within {0 . . . 14} for the primary        transport block,    -   CQI₂ is a CQI index within {0 . . . 14} for the secondary        transport block, and    -   CQI is an 8-bit CQI value for one or two transport blocks.

In the design shown in equation (4), a CQI value within a range of 0through 30 is used to convey a CQI index for one transport block, and aCQI value within a range of 31 through 255 is used to convey two CQIindices for two transport blocks. The UE may also map the CQI index orindices for one or two transport blocks to a single CQI value in othermanners. Computer simulations indicate that an 8-bit CQI value for oneor two transport blocks can provide sufficiently accurate CQIinformation and good data performance. However, fewer or more bits mayalso be used for the CQI value.

FIG. 5 shows a design for sending PCI and CQI information on theHS-DPCCH. In each TTI, ACK/NACK information may be sent in the firstslot of the TTI, and the PCI and CQI information may be sent in thesecond and third slots of the TTI. In each TTI, one ACK/NACK bit for onetransport block or two ACK/NACK bits for two transport blocks may bechannel encoded to obtain 10 code bits. The 10 code bits for ACK/NACKmay be spread and mapped to the first slot of the TTI.

In one design, a PCI/CQI report includes two bits for PCI informationand 8 bits for CQI information, which may comprise one 8-bit CQI valuecomputed as shown in equation (4). The ten bits for the PCI/CQI reportmay be channel encoded with a (20, 10) block code, which may be amodified Reed-Muller (RM) code, to obtain a codeword of 20 code bits.The 20 code bits for the PCI/CQI report may be spread and mapped to thesecond and third slots of the TTI.

The Node B may receive the PCI/CQI report from the UE and determinewhether the UE prefers one or two transport blocks and the CQI index foreach preferred transport block based on the reported CQI value. The NodeB may transmit the number of transport blocks preferred by the UE orfewer transport blocks. For example, if the UE prefers two transportblocks, then the Node B may transmit zero, one, or two transport blocksto the ULE.

The UE may determine the CQI index for each transport block based onP_(OVSF), which may be determined based on the designated number of OVSFcodes, M. The Node B may have K OVSF codes available for the HS-PDSCH,where K may or may not be equal to M. If K=M , then the Node B maytransmit each transport block with the K OVSF codes at P_(OVSF) to theUE.

If K<M, then in one design the Node B may scale down the transport blocksize by a factor of K / M and may transmit a transport block of asmaller size with the K OVSF codes at P_(OVSF) to the UE. For example,if K=10, M=15, and a transport block size of S is selected by the UE,then the Node B may transmit a transport block of size 10·S/15 with 10OVSF codes at P_(OVSF) to the UE. This design may ensure that the SINRof the transmitted transport block closely matches the SINR estimated bythe UE since the same P_(OVSF) is used for both SINR estimation by theUE and data transmission by the Node B. In another design, the Node Bmay scale up P_(OVSF) by a factor of up to M/K and may then transmit atransport block of size S or larger at the higher P_(OVSF) to the UE.The Node B may predict the improvement in SINR with the higher P_(OVSF)and may select the transport block size accordingly.

If K>M, then in one design the Node B may scale up the transport blocksize by a factor of K/M and may transmit a transport block of a largersize of K·S/M with the K OVSF codes at P_(OVSF) to the UE. In anotherdesign, the Node B may scale down P_(OVSF) by a factor of up to M/K andmay then transmit a transport block of size S or smaller at the lowerP_(OVSF) to the UE.

FIG. 6 shows a design of a process 600 performed by the UE (or areceiver). Signaling indicating the available transmit power may bereceived from the Node B (or a transmitter) or may be obtained in someother manner (block 612). A transmit power per channelization code maybe determined based on the available transmit power and the designatednumber of channelization codes (block 614). The available transmit powermay be the actual transmit power for data transmission. Alternatively,the available transmit power may be a hypothetical value to use indetermining the transmit power per channelization code and may bepotentially different from the actual transmit power. For example, theNode B may use all of its available transmit power on less than thedesignated number of channelization codes, and the available transmitpower for the designated number of channelization codes may be ahypothetical value that is greater than the transmit power actuallyavailable at the Node B. A channelization code may be an OVSF code orsome other type of code. The designated number of channelization codesmay be the maximum number of channelization codes (which is 15 in HSDPA)or some other fixed number of channelization codes that is known by boththe UE and the Node B. The designated number of channelization codes mayalso be obtained via signaling from the Node B. The transmit power perchannelization code may be determined by uniformly distributing theavailable transmit power across all transport blocks and across thedesignated number of channelization codes.

Multiple CQI indices for multiple transport blocks to be sent inparallel in a MIMO transmission may be determined based on the transmitpower per channelization code (block 616). For block 616, the SINRs ofthe multiple transport blocks may be estimated based on the transmitpower per channelization code. The SINRs may then be mapped to CQIindices based on a CQI mapping table for the designated number ofchannelization codes. The CQI mapping table may be one of multiple CQImapping tables for (i) different designated numbers of channelizationcodes and/or (ii) different mappings of transport block parameters toCQI levels for the designated number of channelization codes.

The multiple CQI indices may be sent to the Node B (block 618).Thereafter, multiple transport blocks may be received via the designatednumber of channelization codes from the Node B (block 620). Thetransport blocks may be transmitted at the transmit power perchannelization code by the Node B. Alternatively, the multiple transportblocks may be received via a second number of channelization codes,which may be fewer or more than the designated number of channelizationcodes. The sizes of the transport blocks and/or the transmit power perchannelization code may be scaled up or down based on the designatednumber of channelization codes and the second number of channelizationcodes.

FIG. 7 shows a design of a process 700 performed by the Node B (or atransmitter). Signaling indicating the available transmit power may besent to the UE (or a receiver) (block 712). Signaling indicating thedesignated number of channelization codes may also be sent to the UE.Alternatively, the UE may already know the designated number ofchannelization codes. Multiple CQI indices for multiple transport blocksmay be received from the UE (block 714). The CQI indices may bedetermined by the UE based on the transmit power per channelizationcode, which may be determined based on the available transmit power andthe designated number of channelization codes.

Multiple transport blocks may be sent in a MIMO transmission to the UEbased on the multiple CQI indices (block 716). In one design, themultiple transport blocks may be sent with the designated number ofchannelization codes and at the transmit power P_(OVSF) perchannelization code to the ULE. In another design, the sizes of thetransport blocks may be scaled up or down based on the designated numberof channelization codes and a second number of channelization codes. Thetransport blocks may then be sent with the second number ofchannelization codes and at the transmit power P_(OVSF) perchannelization code to the UE. In yet another design, the transmit powerper channelization code may be scaled up or down based on the designatednumber of channelization codes and the second number of channelizationcodes. The transport blocks may then be sent with the second number ofchannelization codes and at the scaled transmit power per channelizationcode to the UE.

For symmetric code allocation, the Node B may send each transport blockwith a common set of channelization codes. For asymmetric codeallocation, the Node B may send one transport block (e.g., a primarytransport block) with a set of channelization codes and may send anothertransport block (e.g., a secondary transport block) with a subset ofthis set of channelization codes.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the disclosure herein may be implemented as electronichardware, computer software, or combinations of both. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits, and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the disclosure herein may be implemented or performedwith a general-purpose processor, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source using a coaxial cable, fiber optic cable,twisted pair, digital subscriber line (DSL), or wireless technologiessuch as infrared, radio, and microwave, then the coaxial cable, fiberoptic cable, twisted pair, DSL, or wireless technologies such asinfrared, radio, and microwave are included in the definition of medium.Disk and disc, as used herein, includes compact disc (CD), laser disc,optical disc, digital versatile disc (DVD), floppy disk and blu-ray discwhere disks usually reproduce data magnetically, while discs reproducedata optically with lasers. Combinations of the above should also beincluded within the scope of computer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the scope of thedisclosure. Thus, the disclosure is not intended to be limited to theexamples and designs described herein but is to be accorded the widestscope consistent with the principles and novel features disclosedherein.

1. An apparatus for wireless communication, comprising: at least oneprocessor configured to determine a transmit power per channelizationcode based on a designated number of channelization codes, to determinemultiple channel quality indicator (CQI) indices for multiple transportblocks based on the transmit power per channelization code, and to sendthe multiple CQI indices to a Node B; and a memory coupled to the atleast one processor.
 2. The apparatus of claim 1, wherein the at leastone processor is configured to receive signaling indicating thedesignated number of channelization codes.
 3. The apparatus of claim 1,wherein the designated number of channelization codes is a maximumnumber of channelization codes available for sending the multipletransport blocks.
 4. The apparatus of claim 1, wherein the designatednumber of channelization codes is a fixed number of channelization codesavailable for sending the multiple transport blocks and known a priori.5. The apparatus of claim 1, wherein the at least one processor isconfigured to receive signaling indicating available transmit power andto determine the transmit power per channelization code based further onthe available transmit power.
 6. The apparatus of claim 5, wherein theat least one processor is configured to determine the transmit power perchannelization code by uniformly distributing the available transmitpower across the multiple transport blocks and across the designatednumber of channelization codes.
 7. The apparatus of claim 5, wherein theavailable transmit power is a hypothetical value to use in determiningthe transmit power per channelization code and is potentially differentfrom actual transmit power for data transmission.
 8. The apparatus ofclaim 1, wherein the at least one processor is configured to estimatesignal-to-interference-and-noise ratios (SINRs) of the multipletransport blocks based on the transmit power per channelization code,and to determine the multiple CQI indices for the multiple transportblocks based on the SINRs.
 9. The apparatus of claim 1, wherein the atleast one processor is configured to determine the multiple CQI indicesfor the multiple transport blocks based on a CQI mapping table for thedesignated number of channelization codes.
 10. The apparatus of claim 9,wherein the CQI mapping table is one of multiple CQI mapping tables fordifferent designated numbers of channelization codes.
 11. The apparatusof claim 9, wherein the CQI mapping table is one of multiple CQI mappingtables for different mappings of transport block parameters to CQIlevels for the designated number of channelization codes.
 12. Theapparatus of claim 1, wherein the at least one processor is configuredto receive the multiple transport blocks from the Node B, the transportblocks being transmitted at the transmit power per channelization codeor higher by the Node B.
 13. The apparatus of claim 1, wherein the atleast one processor is configured to receive the multiple transportblocks via the designated number of channelization codes.
 14. Theapparatus of claim 1, wherein the at least one processor is configuredto receive the multiple transport blocks via a second number ofchannelization codes from the Node B, the multiple transport blockshaving sizes scaled based on the designated number of channelizationcodes and the second number of channelization codes.
 15. A method forwireless communication, comprising: determining a transmit power perchannelization code based on a designated number of channelizationcodes; determining multiple channel quality indicator (CQI) indices formultiple transport blocks based on the transmit power per channelizationcode; and sending the multiple CQI indices to a Node B.
 16. The methodof claim 15, wherein the determining the transmit power perchannelization code comprises receiving signaling indicating availabletransmit power, and determining the transmit power per channelizationcode by uniformly distributing the available transmit power across themultiple transport blocks and across the designated number ofchannelization codes.
 17. The method of claim 15, wherein thedetermining the multiple CQI indices comprises estimatingsignal-to-interference-and-noise ratios (SINRs) of the multipletransport blocks based on the transmit power per channelization code,and determining the multiple CQI indices for the multiple transportblocks based on the SINRs.
 18. The method of claim 15, furthercomprising: receiving the multiple transport blocks via the designatednumber of channelization codes from the Node B, the transport blocksbeing transmitted at the transmit power per channelization code orhigher by the Node B.
 19. The method of claim 15, further comprising:receiving the multiple transport blocks via a second number ofchannelization codes from the Node B, the multiple transport blockshaving sizes scaled based on the designated number of channelizationcodes and the second number of channelization codes.
 20. An apparatusfor wireless communication, comprising: means for determining a transmitpower per channelization code based on a designated number ofchannelization codes; means for determining multiple channel qualityindicator (CQI) indices for multiple transport blocks based on thetransmit power per channelization code; and means for sending themultiple CQI indices to a Node B.
 21. The apparatus of claim 20, whereinthe means for determining the transmit power per channelization codecomprises means for receiving signaling indicating available transmitpower, and means for determining the transmit power per channelizationcode by uniformly distributing the available transmit power across themultiple transport blocks and across the designated number ofchannelization codes.
 22. The apparatus of claim 20, wherein the meansfor determining the multiple CQI indices comprises means for estimatingsignal-to-interference-and-noise ratios (SINRs) of the multipletransport blocks based on the transmit power per channelization code,and means for determining the multiple CQI indices for the multipletransport blocks based on the SINRs.
 23. The apparatus of claim 20,further comprising: means for receiving the multiple transport blocksvia the designated number of channelization codes from the Node B, thetransport blocks being transmitted at the transmit power perchannelization code or higher by the Node B.
 24. The apparatus of claim20, further comprising: means for receiving the multiple transportblocks via a second number of channelization codes from the Node B, themultiple transport blocks having sizes scaled based on the designatednumber of channelization codes and the second number of channelizationcodes.
 25. A computer program product, comprising: a computer-readablemedium comprising: code for causing at least one computer to determine atransmit power per channelization code based on a designated number ofchannelization codes; code for causing the at least one computer todetermine multiple channel quality indicator (CQI) indices for multipletransport blocks based on the transmit power per channelization code;and code for causing the at least one computer to send the multiple CQIindices to a Node B.
 26. An apparatus for wireless communication,comprising: at least one processor configured to receive multiplechannel quality indicator (CQI) indices for multiple transport blocksfrom a user equipment (UE), and to send the multiple transport blocks tothe UE based on the multiple CQI indices, the multiple CQI indices beingdetermined by the UE based on a transmit power per channelization code,and the transmit power per channelization code being determined based ona designated number of channelization codes; and a memory coupled to theat least one processor.
 27. The apparatus of claim 26, wherein the atleast one processor is configured to send signaling indicating availabletransmit power, and wherein the transmit power per channelization codeis determined by the UE based further on the available transmit power.28. The apparatus of claim 26, wherein the at least one processor isconfigured to send signaling indicating the designated number ofchannelization codes.
 29. The apparatus of claim 26, wherein the atleast one processor is configured to send the multiple transport blockswith the designated number of channelization codes and at the transmitpower per channelization code or higher to the UE.
 30. The apparatus ofclaim 26, wherein the at least one processor is configured to scalesizes of the multiple transport blocks based on the designated number ofchannelization codes and a second number of channelization codes, and tosend the multiple transport blocks with the second number ofchannelization codes and at the transmit power per channelization codeor higher to the UE.
 31. The apparatus of claim 27, wherein the at leastone processor is configured to scale the transmit power perchannelization code based on the designated number of channelizationcodes and a second number of channelization codes, and to send themultiple transport blocks with the second number of channelization codesand at the scaled transmit power per channelization code to the UE. 32.The apparatus of claim 26, wherein the at least one processor isconfigured to send each of the multiple transport blocks with a commonset of channelization codes.
 33. The apparatus of claim 26, wherein themultiple transport blocks comprise first and second transport blocks,and wherein the at least one processor is configured to send the firsttransport block with a set of channelization codes, and to send thesecond transport block with a subset of the set of channelization codesused for the first transport block.
 34. A method for wirelesscommunication, comprising: receiving multiple channel quality indicator(CQI) indices for multiple transport blocks from a user equipment (UE),the multiple CQI indices being determined by the UE based on a transmitpower per channelization code, and the transmit power per channelizationcode being determined based on a designated number of channelizationcodes; and sending the multiple transport blocks to the UE based on themultiple CQI indices.
 35. The method of claim 34, further comprising:sending signaling indicating available transmit power, and wherein thetransmit power per channelization code is determined by the UE basedfurther on the available transmit power.
 36. The method of claim 34,wherein the sending the multiple transport blocks comprises sending themultiple transport blocks with the designated number of channelizationcodes and at the transmit power per channelization code or higher to theUE.
 37. The method of claim 34, wherein the sending the multipletransport blocks comprises scaling sizes of the multiple transportblocks based on the designated number of channelization codes and asecond number of channelization codes, and sending the multipletransport blocks with the second number of channelization codes and atthe transmit power per channelization code or higher to the UE.
 38. Anapparatus for wireless communication, comprising: means for receivingmultiple channel quality indicator (CQI) indices for multiple transportblocks from a user equipment (UE), the multiple CQI indices beingdetermined by the UE based on a transmit power per channelization code,and the transmit power per channelization code being determined based ona designated number of channelization codes; and means for sending themultiple transport blocks to the UE based on the multiple CQI indices.39. The apparatus of claim 38, further comprising: means for sendingsignaling indicating available transmit power, and wherein the transmitpower per channelization code is determined by the UE based further onthe available transmit power.
 40. The apparatus of claim 38, wherein themeans for sending the multiple transport blocks comprises means forsending the multiple transport blocks with the designated number ofchannelization codes and at the transmit power per channelization codeor higher to the UE.
 41. The apparatus of claim 38, wherein the meansfor sending the multiple transport blocks comprises means for scalingsizes of the multiple transport blocks based on the designated number ofchannelization codes and a second number of channelization codes, andmeans for sending the multiple transport blocks with the second numberof channelization codes and at the transmit power per channelizationcode or higher to the UE.